1. Field of the Invention
This invention relates generally to a process and apparatus for controlling the air flow at the intake of a heat engine and more particularly to a process and apparatus for controlling the air flow of a heat engine of a motor vehicle fed by fuel injection in which the air flow is controlled as a function of rotational speed of the engine, especially near the rated rotational idling speed.
2. Discussion of Background
It is known that the idling speed of a heat engine is traditionally controlled mainly by the air flow in the intake pipe. By correctly controlling the richness and advance, a stable rotational speed is successfully obtained in the absence of external disturbances. On the other hand, when a heat engine requires additional power to operate a peripheral element, such as, for example, power steering or other element, the idling balance is disturbed and the static timing of the speed cannot compensate for the imposed load variation.
In order to reestablish the idling speed of such a heat engine, prior art devices have used an actuator to modify the air flow in the intake pipe. Controlling this actuator makes it possible to maintain an idling speed independently of conditions external to the heat engine and to obtain more stable idling by compensating for inevitable small variations in the engine. The control of the air flow can be realized in different ways. For example, it is possible to control an independent valve used as a bypass on the main intake flow of the engine. It is also possible to act directly on the butterfly valve connected to the accelerator control of the vehicle.
In prior art devices of this type, the control of the engine rotational speed by the actuator is therefore similar to a servo system of the air flow at the intake. However, problems are encountered when trying to put such devices into practice, particularly during transient phenomena. Actually, it is difficult for standard type controls to differentiate between an idling stabilizing action and a poorly defined transient phenomena that can exist in a heat engine. This is particularly the case during a rapid deceleration of the heat engine which can cause the speed of the engine to drop greatly below normal speeds or even cause a complete stall with the engine stopping.